The invention relates to a protective circuit for at least one manually controllable adjusting device for vehicle seats which are driven by an electric motor.
In the known adjusting devices of this type, fuses are used to protect electric motors, conductors and switches. The protection attained thereby, however, is unsatisfactory, not only in seats having multiple adjusting devices necessitating separate protection of each motor, but even in cases where only a single adjusting device is present. The response value of the fuses must be selected so that the fuses respond, requiring their replacement, as seldom as possible. Therefore, relatively high currents can occur which can result in high thermal loads, which, in adjustment devices having an adjustment path limited by a stop, can also result in high mechanical loads because of the high rest torque of electric motors. The high currents also result in the fact that, in cases involving multiple adjusting devices where it is desired to avoid conductors having an extraordinarily large cross section, the electrical circuits of the individual electric motors must also be formed with separate conductors in those sections that are common to all of the electrical circuits. Above all, this complicates the placement and installation of the conductors leading to the manually activatable switches often found at the side of seats. The above-described problem could be solved by mutually, mechanically locking the manually activatable switches associated with the individual adjusting devices in such a manner that only a single switch can be activated at any given time. However, switches of this type are expensive and subject to malfunction. In addition, a simultaneous activation of two adjusting devices, such as is often necessary for an adjustment of the seat height, is precluded.